1. Field of the Invention
This invention relates to an automatic fire extinguishing system in which at least two fire detecting sensors such as infrared detectors detect the position of a fire source and extinguishant discharge from a nozzle is directed towards the fire source.
2. Description of Prior Art
As an automatic fire extinguishing system which detects a fire and carries out fire extinguishing operation automatically, there has been widely known a sprinkler system. This sprinkler system, however, has the disadvantage that a considerable number of sprinkler heads should be provided so as to cover all over the region to be protected in preparation for a fire which will occur at a random position in the region. As a result, the system should inevitably be extensive and complicated in piping installation thereof.
To solve these problems, there have been proposed many systems in which not only a fire occurrence but a direction of a fire source is detected by a fire detecting sensor and a discharge nozzle is adjusted so as to be directed towards the detected fire source as disclosed for example in U.S. Pat. No. 3,752,235. These systems are advantageous as compared with the previous sprinkler system in that a reduced number of discharge nozzles can cover the region to be protected.
However, these conventional systems detect only the occurrence of a fire and the direction of the fire source, and they never detect a distance to the fire source. Thus, they fail to determine the accurate position of the fire source. More particularly, a fire does not always start on the floor as shown by a in FIG. 1, but it sometimes starts at the height h from the floor as shown by b in FIG. 1. When the fire source is on the floor as shown by a, a fire detecting sensor c detects the angle .alpha..sub.1 of the fire source a and a nozzle d is directed towards the fire source a according to the detected angle .alpha..sub.1. In this case, extinguishant discharged from the nozzle d can hit the fire source a. When the fire source is at the height h from the floor as shown by b, the fire detecting sensor c detects the angle .alpha..sub.2 of the fire source and the nozzle d is adjusted to the detected angle .alpha..sub.2. In this case, however, the automatic fire extinguishing system cannot determine the position of the fire source b because the height h of and the distance l to the fire source b are not known and extinguishant discharged is directed towards b' which is an intersect of an extended line of angle .alpha..sub.2 and the floor. As a result, the extinguishant cannot hit the fire source b. Thus, accurate fire extinguishing operation is not always expected with the conventional automatic fire extinguishing systems.